Method and apparatus of using an atomizer in a two-phase liquid vapor enclosure

ABSTRACT

A two-phase liquid vapor enclosure is described. The enclosure includes an atomizer to spray fluid onto a heat evaporator surface. Fluid flows through a nozzle which atomizes the fluid into very small droplets. These small droplets vaporize upon reaching the heated evaporator surface. Once the vapor condenses to liquid, the liquid travels within the enclosure to recirculate to the atomizer.

BACKGROUND INFORMATION

Faster and more powerful computer components allow the design and construction of higher performance computing devices. Unfortunately, the use of such faster and more powerful computer components often results in increased heat generation by such computing devices. Thus, improved heat dissipation technology is often needed to maintain operating temperatures of computing devices within the same range as their predecessors or some other acceptable range.

Maintaining operating temperatures of computer system components below certain levels is important to ensure performance, reliability, and safety. Most integrated circuits have specified maximum operating temperatures, above which the manufacturer does not recommend operation. Transistors, the building blocks of integrated circuits, tend to slow down as operating temperature increases. Additionally, integrated circuits may be physically damaged if temperatures elevate beyond those recommended. Such physical damage obviously can impact system reliability.

Typically, heat sinks, fans, and heat pipes are employed to dissipate heat from integrated circuits and other electronic components. Simply increasing the quantity or size of these heat dissipation elements often accommodates increases in heat generation. The relatively small size of some computing devices, however, may complicate heat dissipation by limiting airflow, crowding heat generating components, and reducing the space available for heat dissipation devices. The small size of such devices also may limit the ability to place heat sinks vertically on top of integrated circuits or other heat generating components.

Microelectronic devices generate heat as a result of the electrical activity of the internal circuitry. In order to minimize the damaging effects of this heat, thermal management systems have been developed to remove the heat. Such thermal management systems have included heat sinks, heat spreaders, fans, and various combinations that are adapted to thermally couple with the microelectronic device. With the development of faster, more powerful, and more densely packed microelectronic devices such as processors, improved cooling technology is needed to remove the generated heat to prevent overheating.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features of the invention will be apparent from the following description of preferred embodiments as illustrated in the accompanying drawings, in which like reference numerals generally refer to the same parts throughout the drawings. The drawings are not necessarily to scale, the emphasis instead being placed upon illustrating the principles of the inventions.

FIG. 1 is a diagram of one embodiment of a two-phase liquid vapor enclosure.

FIG. 2 is a diagram of one embodiment of an atomizer in the two-phase liquid vapor enclosure of FIG. 1.

FIG. 3 is a flowchart of two-phase liquid vapor enclosure cooling method, according to one example method.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular structures, architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the various aspects of the invention. However, it will be apparent to those skilled in the art having the benefit of the present disclosure that the various aspects of the invention may be practiced in other examples that depart from these specific details. In certain instances, descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

Two phase (liquid/vapor) devices, heat exchangers and associated techniques are emerging as an improved thermal solution for high-power, densely populated microelectronic devices such as processors and other integrated circuit (IC) dies. One such technique employs an ultrasonic (could be lower frequency also) atomizer in a liquid-vapor cooling system, wherein the coolant undergoes vaporization during the heat transfer process.

FIG. 1 illustrates one embodiment of a heat exchanger 100. As shown, the heat exchanger 100 may include a two-phase liquid vapor enclosure 105 or vapor chamber. The vapor chamber 105 may be in contact with an electronic component 110, such as a central processing unit (CPU). On the bottom surface of the vapor chamber 105 is an evaporator 115 where liquid may absorb the heat from the CPU 110. Absorption of the heat at the evaporator causes the liquid to vaporize to become a gas (vapor may be better) 120.

The vapor travels upwards in the chamber 105 to the top surface of the vapor chamber 105 where a condenser 125 keeps the surface cool. The coolness of the condenser 125 may absorb the heat and enable the vapor to condense into a liquid. Once the vapor condenses into a liquid, the liquid may travel down the side walls of the chamber 105 and return to the evaporator surface 115 and absorb additional heat and vaporize again. The chamber may be in contact with air-side-fins 127. Heat may be dissipated by the conducting fins 127 by air flowing through these fins.

Current systems of heat exchangers 100 may use various types of materials for the fabrication of the vapor chamber 105 such as porous materials or microgroove channels that enable the liquid the travel to the evaporator surface. If the implementation uses a solid material with a lot of pores, capillary forces may pull the liquid to the pores that allow the liquid to travel to the evaporator surface. If the implementation uses a microgroove channel, the groove geometry may enable capillary force to pull the liquid along the channel.

Ideally, it is desired that the whole evaporator surface be at uniform temperature. However, since the heat source 110 may be located in the center, the heat exchanger 100 may need to make sure the liquid reaches the center of the evaporator surface 115 so that it may absorb heat where the surface is the hottest. For the liquid to reach the center of the evaporator surface 115 where the surface is the hottest, the liquid may have to travel across the heat source 110. Thus, in some instances, the liquid, as soon as it starts to travel across the heat source (CPU 110), starts to vaporize. Therefore, all the liquid available to cool the heat source 110 may start to vaporize before it reaches the center of the heat source 110, thus causing a burnout.

To avoid burnout, additional liquid may be added to the chamber 105 such that the whole evaporator surface 115 may be covered by the liquid. However, by adding additional liquid, the chamber 105 may obtain too much liquid on the outer periphery of the heat source 110 such that the chamber 1 05 does not obtain efficient evaporation off of that surface. Thus creating a liquid convection layer that may create a temperature drop. Therefore reducing the efficiency of the evaporator along its outer surface and causing flooding.

What is needed is a balance between flooding and burnout. Ideally what is needed is a very thin uniform layer of liquid over the evaporator surface 115 without having any preheating of the liquid occur prior to the liquid reaching the heat source 110. In addition, preventing the evaporator surface 115 from having a thick liquid layer is also desirable.

FIG. 2 illustrates one embodiment of an atomizer in the two-phase liquid vapor enclosure of FIG. 1. As shown in FIG. 2, a removable atomizing module 130 may be readily inserted into the housing of the chamber 105 and removed therefrom. In this manner, the removable atomizing module 130 may not only be replaced when it does not operate properly, needs to be refitted, or the like, but may also be replaced by an atomizing module which differs from the module which it is replacing, such as by operating at a different frequency when an ultrasonic spray is being produced therein. The particular atomizer device so selected may thus depend upon the frequency required in order to obtain the required uniform droplet spray at the particular conditions involved in each case.

The atomizing module 130 has a fluid inlet 135. The fluid may be any type of liquid 140 or combinations thereof. The fluid inlet 135 intakes the fluid 120 that is vaporized from the evaporator. The atomizing module 130 has at least one atomizing nozzle 145, which may be an ultrasonic atomizer that is turned toward the evaporator surface 115. The nozzle 145 may be in the shape of a disk or any other shape necessary for the implementation. Fluid flow through the nozzle 145 is atomized into particles or droplets 150. Once the liquid particles are atomized, they strike the heated evaporator surface 115 whereupon the particles or droplets 150 absorb heat and evaporate into a vapor.

The atomizing module 130 may be equipped with a diaphragm (not shown) which may be made to vibrate by means of an oscillator at various frequencies. The fluid flow which passes through the nozzle 145 of the atomizing module 130 is broken up by the vibration of the diaphragm into a large number of small droplets.

The preferred embodiment enables the liquid 140 to enter the chamber 105 perpendicular to the surface area of the evaporator 115. By having the liquid 140 come in perpendicular to the surface of the evaporator 115, the liquid may not become preheated prior to reaching the evaporator. This is accomplished by creating very small droplets 150 that are now uniformly sprayed on the surface of the evaporator 115. The small droplets 150 may be about 40 microns in size or even less. It should be noted that the size of the droplets may vary by implementation. These droplets 150 are small enough that they do not create a thick liquid layer. The atomizing module 130 creates ultrasonic vibration to break up the liquid 140 that is traveling through module 130 into very small droplets 150.

In another embodiment, the atomized nozzle 145 may strike the surface to be cooled obliquely at an angle rather than vertically. This may preserve/achieve an optimal homogeneity of the liquid sprayed onto the surface to be cooled.

FIG. 3 provides a flow chart of a two-phase liquid vapor cooling method, according to but one example embodiment. In accordance with this flow chart 300, a heat source 110, when actuated, generates heat, block 302. Liquid 140 is uniformly sprayed over the surface area of the evaporator 115 with an atomizing module 130, block 304. Fluid flows through the nozzle 145 which breaks up the fluid into very small liquid droplets 150. The small droplets of liquid 150 vaporize upon cooling the evaporator surface 115, block 306. The heat is transferred by vapor transport to the condenser, where the vapor condenses on the surface thereof, thus releasing the heat. The vapor condenses into a liquid upon reaching the condensers 125 thus removing the heat from the evaporator 115, block 308. The condensed liquid is then re-circulated by capillary action, or any other method to transport the condensed liquid, back to the fluid inlet 135 of the atomizing module 130 where it is again evaporated, block 310. It should be noted that the process or processes of FIG. 3 may be in continuous loop. The method may be part of a closed-loop or open-loop process. These steps may occur out of sequence or not at all.

Advantageously, in this device the atomizer is used to produce sub 40 micron liquid droplets which are sprayed normal and uniformly normally to the evaporator surface 115. The extremely small liquid droplets 150 may instantaneously vaporize when the liquid comes into contact with the evaporator surface 115, thus leading to very high heat transfer rates. In addition, since this device may operate at 20 KHz frequency range, it may not produce perceptible noise to humans. Also it can be operated at <100 Hz (inaudible) but larger droplets may be obtained.

In FIGS. 1 and 2, the length and width of the heat exchanger 100 may be designed to accommodate different sizes. During design, length and width may be adjusted by varying the dimensions of the heat exchanger's 100 subcomponents in each direction. Those skilled in the art will appreciate that the dimensions may be designed to improve heat transfer in accordance with coolant properties. Though the heat exchanger 100 depicted in this embodiment is rectangle, the shape will generally correspond to the die to which the heat exchanger is thermally coupled and is adaptable. Likewise the atomizer may vary in shape or may embody other geometries to accommodate heat transfer characteristics such as temperature and pressure drop profiles. 

1. A method comprising: generating heat in a microelectronic device; emitting liquid from an atomizing module; and transferring heat from an evaporator surface.
 2. The method of claim 1, further comprising breaking up the liquid flowing in the atomizing module.
 3. The method of claim 2, further comprising vaporizing the liquid upon reaching the evaporator surface.
 4. The method of claim 3, further comprising condensing the vaporized liquid.
 5. The method of claim 4, further comprising releasing heat.
 6. The method of claim 5, further comprising recirculating the condensed liquid to the atomizing module.
 7. The method of claim 6 wherein the method occurs in a continuous loop.
 8. The method of claim 6 wherein the method is part of a closed loop process.
 9. The method of claim 6, wherein the method is part of an open loop process.
 10. The method of claim 1, wherein the emitting the liquid is uniformly emitted from the atomizing module.
 11. A heat exchanger comprising: a vapor chamber; an evaporator coupled to the chamber; and an atomizer module in the housing of the chamber, wherein the module to disperse liquid on the evaporator surface where the liquid absorbs heat and vaporizes.
 12. The heat exchanger of claim 11 further comprising and electronic component coupled to the evaporator, wherein the electronic component to generate heat.
 13. The heat exchanger of claim 12, wherein the heat from the electronic component to heat the evaporator surface.
 14. The heat exchanger of claim 11, further comprising a condenser coupled to the chamber, wherein the vapor travels within the chamber from the evaporator to the condenser.
 15. The heat exchanger of claim 14, wherein the condenser to absorb the heat from the vapor.
 16. The heat exchanger of claim 15, wherein the vapor upon cooling, condenses into a liquid.
 17. The heat exchanger of claim 11, further comprising air side fins, wherein the fins dissipate heat from the chamber by air flow through the fins.
 18. The heat exchanger of claim 11, wherein the atomizer module is removable.
 19. The heat exchanger of claim 11, wherein the atomizer module to operate at varying frequencies.
 20. The heat exchanger of claim 13, wherein the atomizer module includes a nozzle through which the liquid flows.
 21. The heat exchanger of claim 20, wherein the nozzle includes an ultrasonic device to atomize the liquid through the nozzle.
 22. The heat exchange of claim 21, wherein the atomized liquid reaches the heated evaporator surface to absorb the heat and vaporize.
 23. The heat exchanger of claim 22, wherein the atomized liquid is about 40 microns in size.
 24. A atomizing module comprising: a fluid inlet to intake fluid entering the module; and a nozzle coupled to the fluid inlet, wherein the nozzle atomizes the fluid into particles, wherein the particles are dispersed by the module to cool a heated surface.
 25. The atomizing module of claim 24 wherein the nozzle includes a diaphragm to vibrate the nozzle at varying frequencies.
 26. The atomizing module of claim 25, wherein the fluid flow is atomized by the vibrations of the nozzle.
 27. The atomizing module of claim 24, wherein the particles are 40 microns in size.
 28. The atomizing module of claim 24, wherein the nozzle may disperse the particles at various angles.
 29. The atomizing module of claim 24, wherein the particles vaporize upon reaching the heat surface. 